Not that I really need another frequency counter, but it is interesting to see how this one is constructed.
Julian Ilett has a video on a similar kit and his investigation of the circuit was thorough,
including the discovery that the kits available are deritative from original work by Wolfgang “Wolf” Büscher, DL4YHF
(see Frequency counter with a PIC and minimum hardware).
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
